The ancient Romans noted that willow bark can be used to fight fevers.
It turned out that the leaves and bark of the willow tree contain a substance called salicin, a naturally occurring compound similar to acetylsalicylic acid, the chemical name for aspirin.
In 1897, a German chemist with the Friedrich Bayer and Company was searching for a treatment for his father's arthritic pain and began to research acetylsalicylic acid, which worked well. His discovery resulted in the development of a product introduced as Aspirin. By 1899, The Bayer Company was providing aspirin to physicians to give to their patients.
In 1915, aspirin becomes available without a prescription. Today, one can
walk into any pharmacy, supermarket, convenience store or even a newspaper kiosk
and buy over-the-counter pain relievers.

How popular is the use of pain relievers such as aspirins? We will now
refer to the 2004 TGI Chile study. This is a survey of 3,554 persons
between the ages of 12 and 75 conducted in Chile during 2004. Within this
survey, fully 60% of the respondents said that they used a pain reliever in the
last 30 days.

For this article, we are more curious about people who are heavey users of
pain reliever. That is, we wanted to look beyond the person who has the
occasional headache now and then. Rather, we asked our respondents how
many times that they have taken pain relievers in those past 30 days. It
turned out that 21% of the survey respondents said that they took pain relievers
ten or more times. These are people whose lives are encapsulated by the
closing two sentences in Günter Grass' novel örtlich betäubt
(translation: Local Anaesthetic) :"Nichts hält vor. Immer neue
Schmerzen." (translation: Nothing works. There will always be new
pain."

Who are these pain sufferers? The first chart below shows the usage
separately by gender and age. Here are some common perceptions: women
experience more pain than men; women discuss pain more than men; women cope
better with pain than men; women deal with pain differently than men.
There is another common perception that older people experience more pain; this
does not appear to be borne out, but we have to remember that we are referring
solely to over-the-counter non-prescription drugs here.

(Source: 2004 TGI Chile)

The next chart shows the usage by socio-economic level and educational
achievement. It is difficult to come up with a single simple explanation
as to how it is the middle-class that are the heaviest users of pain
relievers. The problem is usage is driven by a number of factors: Do you
think the middle-class experience more painful conditions? Do you think
the middle-class are more conditioned to use over-the-counter pain relievers at
the onset of anything that resembles pain? Do you think the middle-class
are better educated about these over-the-counter medicines than the
lower-class? Do you think the lower-class are less likely to be able to
afford using pain relievers very heavily?